1. Field of the Invention
The invention relates to a driving apparatus and a driving method, and particularly, the invention relates to a driving apparatus and a driving method for driving an LCD.
2. Description of the Prior Art
Liquid Crystal Display (LCD) belongs to the category of flat panel display. Compared with the traditional display, such as cathode ray tube display, the LCD has advantages such as thinner thickness, lower power consumption, no radiation, and LCD is one of the major types of display in market conditions. The display principle of the LCD is inputting voltage by the driving apparatus to change the deflection of the liquid crystal molecules in order to change the polarized characteristics, so as to generate different gray levels when the light emitted by the backlight module passes through the liquid crystal. Therefore, the improvement of the driving apparatus is an important issue of LCD technology.
The driving apparatus of the LCD, especially for thin-film transistor LCD (TFT-LCD), needs buffers for avoiding input signal decaying. In general, the operational amplifiers are often used to be the buffers of the driving apparatus. An output voltage curve could be formed on the loading by providing different voltages to a plurality of buffer and connecting the buffers to the loading. On the other hand, the LCD comprises a plurality of pixels and each of the pixels displays different gray level according to the image wanted to be shown and receives the corresponding voltage from the loading according to the gray level so as to make the liquid crystal molecule corresponding to the pixel deflect to the angle needed.
When the voltage received by the liquid crystal molecule containing the same for a period of time, the characteristics of the liquid crystal molecule would be damaged and then the liquid crystal molecule could not form different gray levels through deflecting to the angles corresponding to different voltages. Therefore, when a pixel needs to show the same gray level and continues to do thus for a period of time, the characteristics of the liquid crystal molecule are easily damaged. To solve the above-mentioned problem, the display voltages of the LCD are separated to both positive and negative polarities according to a reference voltage in the prior art. The positive polarity and negative polarity voltages have one-to-one relations, and the liquid crystal molecules take turns receiving positive polarity voltages and negative polarity voltages. In other words, when a pixel keeps showing the same gray level, the pixel receives positive polarity voltage corresponding to the gray level and negative polarity voltage corresponding to the gray level, so that the liquid crystal molecule would not continuously receiving the same voltage for a long time and causes the characteristics to be damaged.
Besides, for the decreasing of crosstalk phenomenon, the adjacent pixels receive the voltages with opposite polarities. Therefore, two sets of buffers are needed for providing positive polarity and negative polarity voltages at the same time. In the prior art, positive polarity voltages are provided by one of the sets of buffers and negative polarity voltages are provided by another one of the sets of buffers, in other words, a pixel receives positive polarity and negative polarity voltages from the two sets of buffers when the pixel keeps showing the same gray level. However, because the differences of the two sets of buffers of operational amplifiers, the voltage curve formed on the loading would be changed, and when the pixel is requested to show the same gray level, the value of the positive polarity voltage received is different from the value of the negative polarity voltage received by the pixel, so as to lead to the gray level showed by the pixel would be variable, and then the image of the LCD would not meet expectancy.